## Facts

- Plasterers’ Local Union No. 79 and Tile Setters Local Union No. 20 disputed which craft should perform mortaring (“scratch-coat”) work associated with tile and terrazzo installation in Houston.
- The two unions had agreed between themselves to submit jurisdictional disputes to a joint arbitration board, which awarded the disputed work to Plasterers.
- Texas State Tile & Terrazzo Co., Inc. and Martini Tile & Terrazzo Co. (the employers) were not parties to the unions’ arbitration arrangement and assigned the work to Tile Setters under their own collective-bargaining agreements.
- Plasterers picketed the employers to pressure reassignment of the work from Tile Setters to Plasterers.
- Southwestern Construction Co. and one employer filed unfair-labor-practice charges alleging the picketing violated NLRA § 8(b)(4)(D).
- The NLRB conducted a § 10(k) hearing with participation by both unions and both employers and, after considering the arbitration award and other relevant factors, assigned the work to Tile Setters.
- Plasterers refused to indicate compliance with the § 10(k) determination; the NLRB then found Plasterers violated § 8(b)(4)(D) by picketing to force reassignment.
- The D.C. Circuit set aside the NLRB’s order, reasoning that only the rival unions were “parties” to the jurisdictional dispute and that their arbitration agreement barred the Board’s § 10(k) action.

## Issues

1. Whether employers whose work assignments and costs are directly affected are “parties to the dispute” within the meaning of NLRA § 10(k).
2. Whether a voluntary adjustment method agreed to only by the rival unions (and not by the employers) deprives the NLRB of authority to “hear and determine” the jurisdictional dispute under § 10(k).

## Decision

- The Supreme Court reversed the D.C. Circuit and enforced the NLRB’s order.
- The Court held the employers were “parties to the dispute” under § 10(k) because they had substantial financial and operational stakes in the work-assignment outcome.
- Because the employers had not agreed to the unions’ arbitration procedure, the unions’ bilateral arbitration agreement did not bar the NLRB from proceeding under § 10(k).
- The NLRB could consider the union arbitration award as a relevant factor but was not bound by it where nonconsenting employers would be materially affected.
- With the § 10(k) determination valid, Plasterers’ picketing to compel reassignment supported the Board’s finding of a § 8(b)(4)(D) violation.

## Legal Principles

- For NLRA § 10(k), “parties to the dispute” include employers directly affected by a jurisdictional work-assignment controversy when they have substantial financial or operational interests at stake.
- The NLRB’s duty to “hear and determine” a jurisdictional dispute under § 10(k) is displaced only when all parties to the dispute—including affected employers—have adjusted the dispute or agreed on a voluntary adjustment method.
- A union-union arbitration agreement, without employer assent, does not strip the NLRB of § 10(k) jurisdiction.
- The NLRB may weigh an arbitration award among “all other relevant factors” in a § 10(k) decision but is not required to follow it in deciding the work assignment.

## Conclusion

The Court held that affected employers are “parties to the dispute” under § 10(k), so an arbitration mechanism agreed upon only by competing unions does not prevent the NLRB from deciding the jurisdictional dispute and enforcing a resulting § 8(b)(4)(D) unfair-labor-practice order.


NLRB v. Plasterers' Loc. Union No. 79, 404 U.S. 116 (1971)